Op 12-12-16 om 21:35 schreef ville.syrjala@xxxxxxxxxxxxxxx:
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> On VLV/CHV enabling sprite0 when sprite1 has already been enabled may
> lead to an underrun. This only happens when sprite0 FIFO size is zero
> prior to enabling it. Hence an effective workaround is to always
> allocate at least one cacheline for sprite0 when sprite1 is active.
>
> I've not observed this sort of failure during any other type of plane
> enable/disable sequence.
>
> Testcase: igt/kms_plane_blinker
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 24 +++++++++++++++++++++++-
> 1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index fa882cdcac52..75a5bde43723 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -1006,6 +1006,12 @@ static uint16_t vlv_compute_wm_level(const struct intel_crtc_state *crtc_state,
> return min_t(int, wm, USHRT_MAX);
> }
>
> +static bool vlv_need_sprite0_fifo_workaround(unsigned int active_planes)
> +{
> + return (active_planes & (BIT(PLANE_SPRITE0) |
> + BIT(PLANE_SPRITE1))) == BIT(PLANE_SPRITE1);
> +}
> +
> static int vlv_compute_fifo(struct intel_crtc_state *crtc_state)
> {
> struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
> @@ -1016,12 +1022,25 @@ static int vlv_compute_fifo(struct intel_crtc_state *crtc_state)
> int num_active_planes = hweight32(active_planes);
> const int fifo_size = 511;
> int fifo_extra, fifo_left = fifo_size;
> + int sprite0_fifo_extra = 0;
> unsigned int total_rate;
> enum plane_id plane_id;
>
> + /*
> + * When enabling sprite0 after sprite1 has already been enabled
> + * we tend to get an underrun unless sprite0 already has some
> + * FIFO space allcoated. Hence we always allocate at least one
> + * cacheline for sprite0 whenever sprite1 is enabled.
> + *
> + * All other plane enable sequences appear immune to this problem.
> + */
> + if (vlv_need_sprite0_fifo_workaround(active_planes))
> + sprite0_fifo_extra = 1;
I don't think you need crtc_state->active_planes just for this, it adds a lot of tracking for something that could be done by
if (noninverted->plane[SPRITE1] && !noninverted->plane[SPRITE0])
/* allocate 1 for sprite 0 */
Maybe drop that patch?
> total_rate = noninverted->plane[PLANE_PRIMARY] +
> noninverted->plane[PLANE_SPRITE0] +
> - noninverted->plane[PLANE_SPRITE1];
> + noninverted->plane[PLANE_SPRITE1] +
> + sprite0_fifo_extra;
>
> if (total_rate > fifo_size)
> return -EINVAL;
> @@ -1042,6 +1061,9 @@ static int vlv_compute_fifo(struct intel_crtc_state *crtc_state)
> fifo_left -= fifo_state->plane[plane_id];
> }
>
> + fifo_state->plane[PLANE_SPRITE0] += sprite0_fifo_extra;
> + fifo_left -= sprite0_fifo_extra;
> +
> fifo_state->plane[PLANE_CURSOR] = 63;
>
> fifo_extra = DIV_ROUND_UP(fifo_left, num_active_planes ?: 1);
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